1. Field of the Invention
The present invention relates to a method to control a temperature of a laser diode (hereafter denoted as LD) with a thermo-electric controller and a temperature controller that uses the method above.
2. Related Prior Art
Various techniques have been well known to control a temperature of the LD, where the LD is applied in an optical communication with a long range and in a dense wavelength division multiplexed communication. In such application, the emission wavelength of the LD is necessary to be precisely controlled, and a thermo-electric cooler (hereafter denoted as TEC) such as Peltier element has been generally used. The TEC has been feedback controlled by an automatic temperature control (hereafter denoted as ATC) driver in the prior arts.
However, when the target temperature of the TEC and the current temperature thereof are widely different, the TEC-driver is going to supply a large current in the TEC to make the temperature of the TEC close to the target temperature, which is generally called as the rush current. A conventional LD controller has provided a function to limit the rush current, that is, the maximum current able to be brought out from the TEC driver.
Recently, some standards concerning to the control of the LD, in particular the emission wavelength thereof, have ruled the maximum rate of the increment of the TEC driving current. As described, although various circuits that limit the maximum driving current have been well know, any circuit has not realized to restrict the maximum rate of the increment of the TEC driving current.